Synthesis gas, which is also known as syngas, is a mixture of gases comprising primarily of carbon monoxide (CO) and hydrogen (H2), and very often some carbon dioxide. Generally, syngas may be produced from any carbonaceous material. In particular, biomass such as agricultural wastes, forest products, grasses, and other cellulosic material may be converted to syngas.
Syngas is a platform intermediate in the chemical and bio-refining industries and has a vast number of uses. Syngas can be converted into alkanes, olefins, oxygenates, and alcohols such as ethanol. These chemicals can be blended into, or used directly as, diesel fuel, gasoline, and other liquid fuels. Syngas can also be directly combusted to produce heat and power. The substitution of alcohols in place of petroleum-based fuels and fuel additives can be particularly environmentally friendly when the alcohols are produced from feed materials other than fossil fuels.
Improved methods are needed to more cost-effectively produce syngas. Methods are also desired for producing syngas at a greater purity and with desirable ratios of H2 to CO to facilitate the conversion of syngas to other products, such as ethanol.
While residue oil can be upgraded in petroleum refineries via coking process, there is still a substantial need in the art for more efficient and cost effective methods for achieving the resid upgradation. There is also a need to increase the amount of liquid products and to decrease the amount of gas and/or coke make, when upgrading such feedstocks. Delayed Coking & fluid coking processes produces high amount of low value petroleum coke, which is typically 1.5 times of Concarbon, which means, processing of heavy crude oil having 40% VR with 27% Concarbon will produce 16 MT of coke as by product per every 100 MT of crude oil. The price of coke is very low as compared to crude oil price, approximately 1/10th of crude oil price and it erodes the refinery margin heavily. In the current scenario, sustaining the refinery margin in view of ever deteriorating quality of crude oil mainly depends on the profit margin gained from the upgradation of the residue to yield more liquid and less of low value byproducts such as coke.
The greatest challenge in upgradation of highly contaminated residue feedstock is depositing feedstock impurities on the solid particles without slippage of these impurities and achieving sustainable operation with good run length of the unit. Residue contains more concarbon residue and hence requires larger surface for depositing these impurities otherwise the same may deposit on the walls of the reactor leading to shutdown of the unit. Ultimately, it limits the residue content in the feedstock.
Another challenge in in-situ partial regeneration of coke/coke reforming process is maintaining the reaction rate suitable for commercial production of syngas. Coke not only deposits on the outer surface of upgrading material but also deposits in upgrading material pores during residual upgrading processing. The coke deposited on the upgrading material blocks the pores; hence it reduces the overall surface area available for contacting the regeneration agent. As concarbon of residual oil increases, multilayered coke formation/deposition on upgrading material takes place. The multilayer coke difficult to gasify and requires higher temperatures for gasification similar that of petroleum coke gasification. The coke on the upgrading material top layer/surface is easy to react; the remaining inner layer of coke is difficult for regeneration due to increased diffusion resistance. The partial regeneration of top layer of coke follows the homogeneous model while, partial regeneration of inner layer of coke follows shrinking core model with increased diffusion resistance, which is rate determining step.
Therefore, there is a need to upgrade heavy residual oils containing higher Concarbon and metal concentrations to lighter products through a more efficient & cost effective method. Such methods should produce higher valuable products such as higher grade oils, high quality syngas, etc. without producing petroleum coke as by product.